It is known in the construction of large, high-rise commercial or residential buildings to construct a self-supporting structure of a roof, floors and interior bearing members out of concrete and/or steel, and to clad this self-supporting structure with an exterior building envelope enclosure.
Common types of exterior building envelope enclosures known in the art are shown in FIGS. 1A-1D. FIG. 1A is a vertical cross-sectional view of a standard window wall. FIG. 1B is a vertical cross-sectional view of a standard curtainwall. FIGS. 1C and 1D are vertical cross-sectional views of hybrid window/curtain wall systems, which are window walls designed to incorporate curtainwall aesthetics and certain design principles.
These exterior building envelope enclosures typically have simple metal vertical wall structures 10 which are joined to horizontal floor structures (not shown) to create modules. On site, modules vertically and horizontally join and or align to each other with verticals 10 and horizontals (not shown) which incorporate male/female joinery as well as vertical seals.
Architectural fascia materials such as glass 15 can be used at vision and opaque areas, and are typically glazed in the factory but can be site glazed as well.
FIG. 1A shows a typical, window wall assembly, with verticals 10 and horizontals (not shown), which is factory assembled and then site installed between two adjacent concrete floor slabs 16 and sealed with caulking 18 and 18′, respectively, with sub sill receptors 14 and head receptors 12.
During assembly, after the window wall assembly is placed into the sub sill receiver 14, its upper end is then rotated forward into the head receptor extrusion 12. The window wall assembly is prevented from leaning outward by an exterior extruded arm in the head receptor. The extruded arm of the head receptor 12 usually contains seals that make contact with the horizontal top edge of the window wall assembly. The window wall assembly can then be joined to a previously-installed window wall assembly by using male/female vertical 10 with vertical seals. A separate drive-on extrusion may then be driven into the interior side of the head receptor extrusion 12 and locked into place, for example by way of serrated teeth and leverage, while holding the window wall assembly tightly into the head receptor 12. Sealant (not shown) may be applied to critical areas in order to ensure a tight air and water seals.
Typical window wall assemblies, such as the typical window wall assembly shown in FIG. 1A, often require a waterproof membrane which seals the concrete slabs 16. This waterproof membrane is then covered with an insulated external spandrel cover panel 20 to cover the concrete slab 16. The membrane is required since, over time, exterior surface applied seals become compromised, and water is expected to enter through spandrel cover panel 20 and can cause damage to concrete slab 16 over time and simply leak to the interior.
Window wall assemblies as shown in FIG. 1D have a notched vertical bottom and often require a time- and sequence-critical site-installed waterproof membrane. The surface receiving the waterproof membrane must be clear of debris, sufficiently dry, primed and generally prepared, so that the membrane bonds properly to the concrete slab 16 as well as to the module previously installed below. The membrane is required since water is expected to enter through vertical 10 of multiple modules installed on any given floor and is viewed as a design limitation which must be overcome by adding the site-installed waterproof membrane.
With typical window wall assemblies, as shown in FIGS. 1A, when loads, such as wind pressure, are applied to window wall assemblies, water will likely enter the various joinery of vertical and horizontals and the locations where discreet modules vertically join to each other with male/female verticals 10 and vertical seals. This water collects into a sub sill 14 which acts to collect water from multiple modules installed on any given floor.
One problem with typical window walls and their sub sills, such as sub sill 14, is that, depending on wind pressure and volume of water collected, the sub sill may need varying vertical heights in order to properly manage drainage of collected water. This requires various sub sill designs so as to manage different conditions on a given project or the design team will be forced to use the highest performing sub sill so that aesthetics remain constant. However, requiring different sub sill designs on a single project complicates the design of each project and increases inventory requirements, lab testing with various sub sill designs. Often projects default to the highest performing sub sill required on a given project in order to simplify the process even if it compromises optimal aesthetics and thermal performance.
Sub sills with modest vertical heights will not drain collected water as well as those with increased vertical heights. This is because the increase in vertical height presents additional surface area and, therefore, an area for increased thermal exchange. Thermal exchange impacts interior surface temperature conditions of typical sub sills, such that, in cold climates, as the height of the sub sill is increased, the risk of interior water vapor condensing on its interior surfaces, which is an unwanted condition, is also increased. In warm climates, a large sub sill increases interior surface temperature and can result in condensation forming on exterior surfaces, as well as extreme interior hot surfaces, which are unwanted conditions.
Curtain walls, such as in FIG. 1B, and window walls, such as FIGS. 1C and 1D, utilize at least one continuous metal vertical 10 which is connected to horizontals (not shown). The continuous metal vertical design approach increases thermal exchange between architectural shadow box areas, which are often pressure equalized and conditioned to the exterior environment, and framing at vision areas, which are conditioned to the interior environment. This design approach impacts conditions within the shadow box and can present as visual distortions, which is an unwanted condition. This design approach impacts interior surface conditions of vertical 10 and the horizontal (not shown) which acts as a transition between the shadow box and the vision area. In cold climates, it increases the risk of interior water vapor condensing on the interior surfaces of the vision area as entering through small flaws in frame seals and condensing on the interior surfaces of the shadow box, which are unwanted conditions. In warm climates, the continuous vertical increases the interior surface temperature, can promote condensation forming on exterior surfaces and can promote condensation forming on multiple surface areas within the shadow box, which is an unwanted condition.
The rain screen design approach is principally used to protect all types of primary air seals from direct exposure to exterior conditions, such as direct exposure to the sun, water and contaminates deposited by rain and wind, by locating them in a hidden area beyond the outermost exposed exterior surface of exterior building envelope enclosures.
The rain screen approach is viewed as an advanced design approach. Previously, curtainwalls and window walls as depicted in FIGS. 1A-D used an exterior primary weather seal, which was placed on the outermost envelopes surface, and was often referred to as “fish tanking”. These seals placed on the outermost envelopes surface were directly exposed to various weather conditions, including UV from the sun light, and, therefore, required regular maintenance. Today's curtain walls, such as shown in FIG. 1B, and window walls, such as shown FIGS. 1C and 1D, utilize the rain screen design approach to protect the primary vertical and horizontal air seal barriers located behind an exterior face of the vertical and horizontal framing. The primary vertical air seal is site-married to primary horizontal seals with silicone.
The rain screen design approach presents a challenge since often it is difficult to measure the amount of moisture, or other surface contaminant, which may be present on the surfaces of materials to be joined and which can limit optimal adhesion of silicone to substrate surfaces. The silicone often joins to vertical and horizontal frame surfaces which move independent of each other due to thermal cycling, wind, seismic and live loads and for which the joinery and seals are not optimally designed, and these conditions can cause these critical air seals to become compromised.
Another problem with the rain screen approach is that, when structural aluminum framing is being used, the seals' optimal location for thermal control would be on the outermost exterior surface. With the rain screen approach, optimal thermal conditions are not being realized. In cold climates, this increases the risk of condensation collecting on the interior of the building, and in warm climates, this can promote extreme interior surface temperatures and condensation forming on exterior surfaces, which are unwanted conditions.
Thermal problems associated with rain screen designs are viewed as a design limitation which must be overcome by adding exterior factory-extruded compression seals or by increasing the interior aluminum mass. However, adding exterior compression seals requires long term maintenance. In addition, adding aluminum is costly and can create extreme hot spots on the systems' interior surfaces when cold weather transitions to hot weather.
As described, curtain walls such as in FIG. 1B and window walls such as FIGS. 1C and 1D utilize a continuous metal vertical 10 which are connected to horizontals (not shown). The continuous metal vertical design approach increases the chance that sound and heat will travel vertically from one floor to another, an unwanted condition. In order to manage sound traveling, a design limitation, the verticals are often filled with different materials to reduce sound traveling. Often condensation collects in these areas, and creates a risk of mold growth, an unwanted condition.
Curtain walls such as in FIG. 1B and window walls such as FIG. 1C and FIG. 1D utilize a continuous metal vertical 10 which are connected to horizontals (not shown). The continuous metal vertical design approach also increases the chances that sound and/or heat and smoke generated from a fire can travel through the continuous vertical, to floors generally above the sound and fire source, which create life, safety and health issues, can cause other building materials to combust or otherwise be damaged, and can compromise the structural integrity of the vertical which can compromise the vertical's structural connection to the slab 16, all of which are unwanted conditions.
Interior water vapor condensing on visible surfaces is a problem known to many, and design solutions have been substantially resolved and continue to be improved as means, methods and advanced materials prove out and become commercially viable.
Interior water vapor condensing in hidden areas or directly adjacent to hidden areas is a problem that has not received as much attention. These areas are often now being referred to as “outside the mechanical boundary condition” because mechanical engineers cannot easily design a heating system to value this space. Managing this area is left to the designers, façade engineers, assemblers and installers of the exterior building envelope enclosure. The use of internal thermal enhancing materials often referred to as insulation has been used in North America for many decades. These materials, when placed in cavities between the finished space and the exterior wall, or outside the mechanical boundary condition, increase the surface temperature of materials such as finished opaque sheetrock walls. These thermal enhancing materials also have been and continue to be used to reduce outdoor to indoor noise transmission. These materials, however, could have a very detrimental impact on a first condensing surface of exterior building envelope enclosures, such as those depicted in FIGS. 1A-1D. As one adds insulation to cavities between the finished space and the exterior wall, the less conditioned heated air can be absorbed by the first surface to condense.
A global problem with all the conventional exterior building envelope enclosures, such as those depicted in FIGS. 1A-1D, is that they are assembled using structural metal vertical and horizontal framing. Thermal exchange impacts interior surface conditions of structural metal framing at both vision and opaque areas. Opaque or hidden areas present a more profound problem since they are typically outside the mechanical boundary and are encased by finished assemblies, comprised of vertical metal stud and sheetrock. These encased finished assemblies create discrete vertical chambers wherein air is substantially trapped or limited in its ability to promote sufficient convection of tempered air which passes through the sheetrock and to allow any collected water to simply evaporate over time. The interior plane and other tubular surfaces of the structural metal vertical and horizontal framing of the curtainwall and/or window walls are defined as the first surface to condense. In cold climates, structural metal framing increases the risk of interior water vapor condensing on these surfaces, which is an unwanted condition. In warm climates the interior surface temperature increases as a result of the structural metal framing, and cooling systems can promote condensation forming on exterior surfaces, which is an unwanted condition.
A global problem with the sequence of field installation is that site conditions may be optimal for installation of window wall or curtain wall modules but not optimal for application of sealants used to marry vertical and horizontal primary air seals. Often it is difficult to measure the amount of moisture or other surface contaminant which may be present on the surfaces of materials to be joined and which can limit optimal adhesion of silicone to substrate surfaces. Regardless, installation often proceeds, and best efforts are employed by persons skilled and experienced. However, after the installation is completed, checking that all these hidden seals have been optimally applied and have cured properly requires field testing at each location, since they are hidden from view. This is a cost-prohibitive exercise, and, therefore, only random field testing is usually employed. Visual inspection of all critical primary air seals is certainly a preferred path but is not often viable with certain system designs.
FIG. 1E shows conventional metal vertical framing 10. Vertical framing 10 may include a vertical air seal 50 where a site-installed marriage bead is located. Architectural fascia 55 can be attached to the vertical framing 10. FIG. 1F shows conventional metal horizontal framing 65. The horizontal framing 65 may include a horizontal air seal 60 where a site-installed marriage bead is located. Architectural fascia 55 can be attached to the horizontal framing 65.
Repairing or replacing a compromised primary air seal barrier, such as those depicted in FIGS. 1E and 1F, is complicated due to its hidden nature, and often the only corrective measure is to place a seal on the interior surface or access the exterior surfaces of the exterior building envelope enclosure and apply a face seal. Both methods are not preferred remedies and result in unwanted conditions.
Window wall systems which use non-structural insulated panels to enclose a building are typically fastened, from the exterior, to at least one interior vertical structural metal stud. Accessing this fastening location from the exterior is time consuming, increases insurance exposures, is impacted by weather, and requires specialized equipment to access it with either pipe scaffolding, man lifts and hanging scaffolds. Furthermore, insulation connected to a metal layer, or sandwiched between two metal layers, can be damaged when site drilling through the insulated panel. Fastening from the exterior requires multiple steps and are typically as follows. Step 1—Pre-drill an oversized access hole in the insulated panel. Step 2—Place a self-drilling fastener into the access hole. Step 3—Drill fastener and thread the interior vertical metal reinforcement. Step 4—Place leveling shims. Step 5—Properly torque the fastener to join the insulated panel to the interior vertical metal reinforcement. The requirement for multiple steps complicates the process and requires multiple tools, drill bits and careful attention. Additionally, the next panel cannot be installed until these steps are completed, and this, therefore, presents the risk of slowing down the process. Also, for example, when typical fasteners are tightened, the outer metal layer of the insulated panel can be displaced radially inward, such that the insulation can yield and the insulated panel can be compromised, which are unwanted conditions.
Accordingly, there is a need for a spandrel assembly which incorporates an architectural fascia, such as glass, head receptors and sub-sills with a modest vertical height and other built-in design methods to promote water drainage and drying of drainage path in all weather conditions, and pre-installed fasteners.
Accordingly, there is a need for a window wall assembly with architectural fascia such as glass and without structural metal vertical and horizontal frame parts.
Accordingly, there is a need for a window wall assembly with primary air seals placed on the interior, and sealed so they will not substantially impact the thermal properties, wherein the primary air seals can be installed when the exterior building envelope enclosure is substantially completed and interior conditions are optimal for cleaning and preparing surfaces which will receive primary seals. This allows for visual inspection of all primary air seals, along with random field testing by an independent laboratory as may be required.
Accordingly, there is a need to provide an exterior building envelope enclosure that allows for optimal indoor air quality. With optimal relative humidity levels being a large component of indoor air quality, the elimination of metal vertical and horizontal framing from window walls reduces risk. Optimal indoor air quality with optimal relative humidity levels must be achieved without increasing risk of water vapor condensing on interior surfaces of the exterior building envelope enclosure and introducing great risks associated with mold growth.